Automatic control of inverters



Jan. 12, 1960 CHOKU TAKAHASHI 2,921,235

AUTOMATIC CONTROL OF INVERTERS Filed Dec. 18, 1958 Inventor C TAKAHASHI Attorney 2,921,235 Patented Jan. 12, 1960 AUTOMATHI CONTROL OF RTERS Choku Tairahashi, Tokyo, Japan, assignor to Nippon Electric Company, Limited, Tokyo, Japan, a corpora tion of Japan Application December 18, 1958, Serial No. 781,342

Claims priority, application Japan December 26, 1957 1 Claim. (Cl. 315166) This invention relates to inverters and in particular to automatic control circuits therefor. A conventional inverter comprising gas discharge tubes (so-called thyratrons) occasionally malfunctions in that one or both of the tubes continue to conduct when the input signal is removed, when it is re-impressed or when the load impedance suddenly varies.

The object of this invention is to prevent such malfunctioning by keeping the inverter in its preparatory state when it is not in normal operation whereby it starts automatically when normal operation is desired.

According to the invention the inverter is provided with a circuit and discriminating relay for determining whether or not there is an input signal applied to the grid circuits of the gas tubes and for stopping the operation of the inverter when there is no input signal. There is also a circuit and discriminating relay for determining whether or not there is an output alternating current obtained as the result of the operation of the inverter and for disconnecting the power supply to the inverter when there is an input signal without an output current.

The above-mentioned and other features and objects of this invention will become apparent by reference to the following description of the invention taken in conjunction with the accompanying drawing of a preferred embodiment thereof.

In the drawing, 1 shows the input terminals, 2 an input transformer, 3 and 4 the hot cathode grid control discharge tubes, 5 a grid bias voltage, 6 the extinction condenser, 7 an output transformer, 8 the input signal discriminating relay, 9 a slow-acting relay, 10 a voltage source for the slow-acting relay 9, 11 the output signal discriminating relay, i2 and 13 full wave rectifiers for the relay sources, 14 the output terminals and 15 the D.-C. plate voltage source terminal.

If a signal is applied to input terminals 1, it is applied to the grids of discharge tubes 3 and 4 through input transformer 2 and excites the tubes. The input signal also causes the input discriminating relay 8 to operate through the input transformer 2 The contact 8a closes by the operation of the relay 8 and connects the plate voltage source 15 to the discharge tubes. This places the inverter in operation.

The inverter output is connected through the output transformer '7 to the output terminals 14 and is also applied to the output discriminating relay 11 through rectifier 13. The contact 11a closes by operation of the relay it before the slow-release acting relay 9 operates. The contact 9a is then opened by the release of the relay 9 and the inverter is in the normal condition of operation.

When the input signal is broken the discriminating relay 8 is deenergized and the contact 3a opens. The in- 0 verter is now in the preparatory condition of operation.

With the inverter in the normal condition of operation, should there be trouble, such as might occur due to the simultaneous ignition of discharge tubes 3 and 4 resulting from the rapid variation of the load impedance, the output current falls to zero even though the input signal is applied. The discriminating relay 11 is deenergized and the contact Ha opens. As a result of this operation the input signal discriminating relay 3 is deenergized and the operation of inverter ceases. Also the contact 311 closes, the slow-acting relay 9 operates, the contact 9a closes and the input signal is again applied to input signal discriminating relay 8. By the operation of the input signal discriminating relay 8, the plate voltage is again applied through the contact $a to the plates of the discharge tubes 3 and 4 (which have now become deionized) and the inverter is again in operating condition. This operation continues automatically until the inverter reaches the normal operating condition.

As above-mentioned, if there is any trouble the inverter returns automatically to normal condition by again going through its operating cycle until it ride itself of any defect hitherto experienced thereby increasing stability.

While I have described above the principles of my invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of my invention as set forth in the objects thereof and in the accompanying claim.

What is claimed is:

In an inverter employing hot cathode grid controlled gas discharge tubes in a push-pull circuit arrangement including an input circuit, an output circuit and a power supply therefor; means for automatically controlling the operation of said inverter comprising a first relay means coupled to said input circuit and operative in response to a signal applied thereto to connect said power supply to said inverter, second relay means coupled to said output circuit and responsive to current flowing therein to close a holding circuit for maintaining said first relay means in the operated condition, a third relay means having slow release charcteristics coupled in operative relation to said first relay means and operative on energization of the latter by the input signal to open a circuit connected in parallel to said holding circuit.

No references cited. 

